The main story is probably 30 hours if you just focus on that. Probably longer, depending on your grinding efficiency. The art style is very bright and pleasing, the combat is fun, and there are six main characters to choose from over the course of the game.
There are lot of story there if you want to sit through all of the text (some of it poorly translated, but still). Most of the side quests are either fetch quests, talking to people four feet away from each other, or "kill enough creatures to get X number of semi-rare drops." The side quests are very repetitive, but not at all necessary. And the world is huge.
Considering it's $15, if you like turn based RPGs, you'll more likely than not enjoy it. And if you only kind of like it, it's only $15.
